Safety pen needle assemblies are well known in the art for use with medical injectors, particularly pen injectors. Shielding of a used needle post-injection is provided by such devices. Various configurations for shielding are available, including a displaceable shield relative to the needle hub. U.S. Pat. No. 5,964,731 to Kovelman discloses a shield threaded onto a needle hub. With this configuration, however, the shield must be in its most extreme lowest position, wherein the needle is maximally exposed, for mounting onto a medical injector. As such, a user may inadvertently suffer a needle stick during mounting. Transmission of biological material or disease is not a concern with the needle being in a clean state; however, with a practitioner suffering a needle stick, the pen needle assembly must be disposed of since the needle can not be used subsequently on a patient.